What is that? Is it the outline of a saguaro?
I think I know who made your earrings.
There is a Navajo artist named Jolene or Joleen Yazzie who uses a saguaro as a hallmark.
She works in chip inlay.
This is one of her non-chip-inlay pieces. Click through and look at the saguaro stamp on the reverse of this ring.
Here is one of her chip inlay pieces with her saguaro hallmark.